In recent years, a number of behavioral techniques have been developed and applied as interventions for essential hypertension. To date, relaxation techniques appear to be the most promising. However, the literature is characterized by few controlled outcome studies, limited numbers of subjects, short-term follow-up, and minimal information on the degree to which laboratory training leads to blood pressure reductions which can be observed in the naturalistic setting. In addition, the biochemical, psychological, and psychophysiological effects of these techniques have rarely been evaluated. Such evaluation is necessary to understand the mechanisms through which these procedures exert their therapeutic effects. The proposed study, a large-scale controlled investigation of relaxation techniques in the modification of mild essential hypertension, is designed to address these limitations in the literature. Particular emphasis is placed on evaluating factors contributing to both the process and outcome of the relaxation treatment procedures. The subjects will be 240 individuals from a large industrial setting whose blood pressures are in the mild hypertension range (diastolic blood pressure between 95 and 105 mm Hg). The subjects will be medically evaluated and assigned to one of 6 experimental groups. Those prescribed medication will be placed in the group: 1) Standard Medical Treatment with Hypertension Medication. Those subjects not prescribed medication will receive the standard medical treatment and be randomly assigned to one of five other groups: 2) Standard Medical Treatment without Hypertension Medication, 3) Relaxation Training, 4) Relaxation Training Plus Generalization, 5) Biofeedback-Facilitated Relaxation Training, and 6) Biofeedback-Facilitated Relaxation Training Plus Generalization. Data on psychological characteristics along with psychophysiological and biochemical reactivity to physical and psychological stressors will be obtained at preintervention, postintervention, and one-year followup evaluations. The primary outcome measure, blood pressure readings, will be obtained at the worksite throughout all phases of the study.